What are “nadir,” “near vertical,” and “oblique” views?
Unlike robotic satellites, which look Earthward with a fixed geometry, the human astronaut can look out the window of the spacecraft at any angle. If the astronaut looks toward the nadir of the orbit, he or she is looking directly down at the earth with no tilt angle. If the astronaut looks at some angle off the orbit track, he or she is looking at an oblique angle. Oblique photographs are classified as high oblique if the horizon or atmospheric limb can be seen. Photographs are classified as low oblique if they are intermediate between nadir and high oblique. In the database, the “tilt” field records NV (near vertical) for photos that have a center point within 1 degree latitude and longitude of the spacecraft nadir, HO (high oblique) for photos that include the horizon, and LO (low oblique) for the remaining photos.
